Thermostatically actuated valve for regulating vacuum connections



D. R. FERRIS THERMOSTATICALLY ACTUATED VALVE FOR Oct. 31, 1961REGULATING VACUUM CONNECTIONS Filed March 25, 1959 mw am WF f, MR U .W Wv 0@ wim@ w\\\\\\\\\\wN A7' TURA/ET United States Patent O 3,006,552THERMOSTATICALLY ACTUATED VALVE FOR REGULATING VACUUM CONNECTIONS DavidR. Ferris, Cadillac, Mich., assignor to Kysor Heater Company, Cadillac,Mich.

Filed Mar. 23, 1959, Ser. No. 801,030 11 Claims. (Cl. 236-353) Thisinvention relates to improvements in thermostatically actuated valve forregulating vacuum connections.

The principal objects of this invention are:

First, to provide a relatively simple valve for accurately regulatingthe application of a subatmospheric pressure or vacuum to a pressureresponsive device.

Second, to provide a temperature responsive valve for alternatelyconnecting an abnormal pressure such as a vacuum or atmospheric pressureto a pressure actuated element in which the movement of the valve toshut oit the abnormal pressure also admits atmospheric pressure to theelement and is effected rapidly by a spring after suihcient compressionhas been built up in the spring to cause the valve to tactuate with asnap action.

Tnird, to provide a vacuum valve that is immediately responsive tochanges in temperature of its controlling element .and which is not aptto get out of order.

Fourth, to provide a thermostatically actuated pressure control valvewhich renders practical the useof engine vacuum for regulating theradiator shutter of an automotive vehicle in response to changes intemperature in the cooling jacket of the vehicle engine.

Other objects and advantages of the invention Will be apparent from aconsideration ofthe following description and claims. The drawings ofwhich there is one sheet illustrates a highly practical form of theinvention.

FIG. 1 is a fragmentary longitudinal cross sectional view through -thevalve showing the valve mounted on an internal combustion engine andconnected to a radiator shutter operating mechanism. The engine and theshutter mechanism are shown more or less conventionally.

FIG. 2 is a fragmentary enlarged cross sectional View through thethermo-responsive actuating element of the valve.

FIG. 3 is an enlarged fragmentary cross sectional View through the valveshowing the relationship of the valve seats to each other and to themovable valve element.

The present valve constitutes an improvement on and variation of thetemperature responsive valves shown in Patents 2,105,193, 2,248,094 and2,512,548. Speciiically the present valve assembly is designed to renderthe use of the vacuum in an internal combustion engine intake manifoldsuitable as a source of power for actuating a shutter associated withthe radiator of the engine.

In FIG. 1 there is conventionally illustrated an internal combustionengine having a cylinder block 1 and head 2 with coolant passages 3 3therein. The intake manifold of the engine which is under a vacuum whenthe engine is in operation is conventionally illustrated at 4 and thevalve assembly 5 of the invention is mounted on the head 2 with itsthermo-responsive element 6 projecting into the coolant passage 3. Thevalve 5 is connected to the manifold 4 as a source of vacuum by the pipeor conduit 7 and is further connected by the pipe or conduit 8 to apressure differential power device or motor 9 conventionally illustratedas a diaphragm 10 mounted in a housing and subjected on one side to thepressure existing in the pipe 8. A piston rod 11 projects downwardlyfrom the diaphragm and is connected to the operating bar 12 whichconnects to the brackets 13 secured to the several shutter slats 14. Theshutter slats 14 are pivotally supported at their lower corners as at 15to the fname of a radiator conventionally illustrated at 16. The spring17 in the diaphragm housing 9 biases Mice the piston rod downwardly sothat the shutter slats 14 are normally open when no vacuum is applied tothe conduit 8 and the housing 9. An external spring 18 acting on one ofthe shutter slats assists the spring 17 so that the shutter will failsafe or open in the event of dam-age to the valve or any of itsconnections.

The construction of the valve 5 consists of a housing 19 having athreaded neck 20 engaged through the Wall of the cylinder head 2. Thethermo-responsive element 6 has a tube 21 screwed into the end of theneck 20 and is provided with a hollow head 22 containing a mass 23 ofthermally responsive semi-solid expansible material. When expanded, thematerial 23 presses against the diaphragm 24 and forces the rubberplunger 25 into the neck 21 to eject or extend the push pin 26 towardthe housing 19. The housing 19 defines a central recess 27 with a secondpush pin 270 extending therefrom to the first push pin 26.

The outer end of the recess 2'7 is closed first by an inner valvebushing 28 and an outer bushing 29. The outer bushing 29 is threadedinto the end of the recess in the housing and has an interruptedcylindrical flange 30 bearing against the inner bushing to push theinner bushing into the recess.

'Ihe outer bushing member 29 is provided with a central inner bore 31forming Ia spring cavity the inner end of which forms ya relativelylarge circular valve seat at the junction of the bore and the end of thebushing. The bore 31 communicates with a passage 32 receiving thethreaded coupling 33 for the vacuum supply pipe 7. Opposed to the springcavity 31, the inner valve bushing 28 deiines a circular bore 34 with arelatively small seat around its outer end opening to an enlarged valvecavity 35. As appears most clearly in FG. 3 the valve cavity 35 containsa ball or other type valve 36 that is movable between the small seat atthe end of the passage 34 and the large seat at the end of the springcavity 31. In practice the length of movement of the valve element 36from one seat to the other is maintained at about .005 inch or some suchdistance which is only long enough to break the closure at either seat.

Annular O-rings 37 positioned around the exterior of the bushings 28 and29 .seal the bushings to the inner surface of the recess in the housingon opposite sides of the valve element 36. A radially extending passage38 is formed by the discontinuity in the ange 30 on the valve cavities31 and 35 and an annular passage 39 around the outer bushing. The pipeor conduit 8 communicates with this annular space 39 through thethreaded coupling 40.

The ball valve element 36 is normally biased toward the small seat atthe end of the passage 34 by a spring 41 positioned in the bore 31. Thespring 41 is strong enough to resist the tendency of .the vacuum createdin the engine manifold to unseat the valve from the end of the passage34 and the vacuum of the manifold is thus connected through the radialpassages 38 to the pipe 8 and vacuum motor 9 to raise the diaphragm 1t)and the piston rod 11 and close the shutter slats 14 Whenever the engineis operating and is cold.

Within the recess 27 in the valve body the end of the push pin 270 isprovided with a head 42. The head and therefore the pin are normallypressed toward the thermo element 6 by a spring 43 bearing between thehead 42 and the inner bushing 28. This latter spring compresses thethermally expansible mass in the thermo element as the mass cools. Thehead 42 on the push pin also bears `against a concentrically arrangedinner spring 44 which has its outer end abutted against a head 45 on atappet 45 that is supported in slidable, non-sealable relation in thepreviously delined bore 34 in the inner bushing 28. A spring 47compressed between the bushj ing 28 and the head 45 opposes the actionof the spring 44. The tappet 46 is adapted to project into contact withthe ball valve element 36 and unseat the valve from the relatively smallseat around the passage 34.

Atmospheric pressure is admitted to the cavity 27 withirr the valvehousing through radially extending bores 48 and a fiber lter or screen49 portion over the ends of the bores prevents the entry of dust intothe valve mechanism. With the engine starting from a cold condition thevacuum from the manifold will be connected to the shutter motor 9 aspreviously described and the shutter slats 14 are retained closedpreventing cooling action by the radiator 16. As the temperature of thecollant in the engine rises, heating the thermally expansive mass 23,the push pins 26, 270 and the head 42 will be extended against thecompression of the spring 43. At the same time the inner operatingspring 44 will be compressed against the returning force of the backingspring 47 and the spring 41 until sufficient force is built up inthespring 44 to overcome the combined pressure of springs 41 and 47. Atthis time the spring 44 will move the tappet 46 with a quick snap actionto unseat the ball valve 36 from its seat at the end of the passage 34and move .the valve against the relatively large seat at the end of thespring cavity 31. As the surface of the valve comes in contact with thelarge seat the action of the .vacuum assists in holding the valve to thelarger seat and in speeding the shifting of the valve element. At thistime atmospheric pressure is admitted through the filter 49, passage 48and bore 34 to the valve cavity 35 thus breaking the vacuum through thepipe S to the pressure motor 9 and the springs 17 and 1S function tomove the shutter slats 14 to open position so that the cooling action ofthe radiator is available to prevent over heating of the coolant in thejacket 3 of the engine. The reverse action of the valve when the coolantreaches a predetermined low temperature relaxes the extending pressureson the push pin 270 so that the pressure in the spring 44 is relaxed andthe springs 41 and 47 return the ball valve and the tappet 46 to closeoff the atmospheric air passage 34 and readmit vacuum to the pressuremotor 9.

The valve, as thus described, is relatively inexpensive and easy tomanufacture as the only close tolerances required are the relativelength of the valve cavity 35 and the size of lthe valve element 36compared to the length of the flange 30 on the outer bushing. Onceassembled, there are no parts in the valve assembly that can becomemisplaced. Due to the very short travel of the valve element between itsopposed seats the action of the valve is very rapid and the wear on thevalve element and its associate valve seats is negligible. The valve isthus well adapted to reliably control a radiator shutter within veryclose limits of temperature differential in the coolant of the engine.

The temperature at which the valve will be actuated may be adjusted byscrewing the outer bushing 29 a diierent distance into the end of thehousing. This varies Y the position of the inner bushing 28 and the ballvalve 36 with reference to the push pins 26 and 270. The outer bushingis locked in its adjusted position bythe lock nut 50. Since thesemi-solid expansihle material 23 in the thermal element 22 moves thepin 26 a definite distance for any degree of temperature rise, changingthe position of the ball 36 changes the temperature at which the valvewill operate.

The operating temperature may also be adjusted by varying .the extensionof the neck 21 of the thermo element into the neck of the housing 19.This Varies the temperature at which the irst push pin 26 will beeffective to actuate the second push pin 270. The thermo element islocked in its adjusted position by the lock nut 51. In either case, theouter valve bushing 29 locates the inner bushing 28 relative to thethermo element 6 and simultaneously locates the vacuum or abnormalpressure valve seat around the edge of the bore 31 in predeterminedclosely spaced relation to the Iball valve 36 when the valve is seatedagainst the port at the end of the bore 34.

While the valve is especially adapted for regulating or controllingsub-atmospheric or vacuum pressures, it may also be used to regulatesuper atmospheric pressure applied through the pipe 7. In this lattercase it is desirable to provide an outwardly facing fixed stop orshoulder (not illustrated) in the recess 27 against which the innerbushing 28 is positively seated by pressure of the outer bushing 29.This prevents temperature adjustment by movement of the outer bushingbut prevents the super atmospheric pressure from acting on the innerbushing 28 like a piston to vary the temperature setting of the valve.

Whether the valve is used to control a subatmospheric pressure source ora super atmospheric pressure source, the spring 44 which actuates thetappet 46 and the valve element 56 functions as a yieldable motiontransmitting element between the push pin 279 and the head 45 on thetappet. This is essential to permit unrestricted extension of the pushpin 26 underthe expanding pressure of the semi-solid thermallyexpansible material 23. It should be noted that the power developed byexpansion of the expansible material 23 is substantially greater thanthe resistance created -by any of the springs in the valve so that thesprings are readily compressed and do not aiiect the temperature atwhich the valve operates.

In operation of the valve starting with a cold engine the initialextension of the push pin 270 merely compresses the spring 44suiiciently to overcome the reverse pressure developed by the springs 41and 47. When this resistance is overcome the ball 36 is unseated iiromthe small valve seat around the end of the passage 34 and movesimmediately to the large seat around the end of the bore 31. Onceunseated from the small valve seat atmospheric pressure acts on the ballto quickly seat it against the end yof the vacuum passage thus creatinga snap or quick action in the valve and partially releasing thecompression developed in the spring 41.

If the expansible material 23 in the thermo element body immediatelybegins to cool the push pin 26 is caused to retract by the outer spring43 until the compression in spring 44 is overcome by the spring 311 toreopen the vacuum connection.

What is claimed as new is:

1. A thermally actuated valve for regulating a source of vacuum from aninternal combustion engine manifold in response to the cooling jacket ofthe engine comprising a housing adapted to be threaded into an openingin a Wall of said jacket, a thermally responsive element carried on theend of said housing to project into said jacket and having a mass ofthermally expansible material adapted to push on a push pin positionedin a bore in the end of said housing, a recess in said housing openingto said pin, an air passage with a filter thereover opening from saidrecess to the outside of said housing, a pair of valve bushings arrangedin end to end abutted relation in the opposite end of said recess withthe outer bushing threaded into the housing, means including O-ringsaround said bushings forming seals 4'between the exteriors of thebushings and the wall of said recess, the inner one of said bushingshaving a cavity formed in the end thereof opposed to the other bushing,a ball valve element positioned in said cavity, a guideway extendingaxially through the inner of said bushings from the bottom of saidcavity and having a relatively small valve seat around its outer endadapted to be closed by said valve element, a rst spring compressedbetween said inner bushing and said push pin t-o return the pin when thethermal element cools, a tappet slidably and non-sealingly positioned insaid guideway and adapted to contact and unseat said valve element fromsaid small seat, a second spring abutted between said push pin and saidtappet, a third spring abutted between saidtappet and said inner bushingand opposing said second spring, a passage formed in the outer bushingand having a relatively large valve seat formed around its inner end andspaced from said small seat by a distance about .005 inch greater thanthe effective length of said valve element to be closed by the valveelement when the latter is unseated from the small seat by said tappet,said passage in said outer bushing being adapted to be connected to themanifold of said engine, a fourth spring biasing said valve elementtoward said small seat, and means forming a flow passage through saidouter bushing and said housing from said cavity and between said sealsand adapted at its outer end for connection to a shutter actuatingpressure operated device.

2. A thermally actuated valve for regulating a source of vacuum from aninternal combustion engine manifold in response to the temperature inthe cooling jacket of the engine comprising a housing adapted to bethreaded into an opening in a wall of said jacket, a thermallyresponsive element carried on the end of said housing to project intosaid jacket and having a mass of thermally expansible material adaptedto push on a push pin positioned in a bore in the end of said housing, arecess in said housing opening to said pin, an air passage opening fromsaid recess to the outside of said housing, a pair of valve bushingsarranged in end to end relation in the opposite end of said recess,means forming seals between the exterior of the bushings and the wall ofsaid recess, one of said bushings having a cavity formed in the endthereof opposed to the other bushing, a ball valve element positioned insaid cavity, a guideway extending axially through the inner of saidbushings and having a relatively small valve seat around its outer endadapted to be closed by said valve element, a rst spring compressedbetween said inner bushing and said push pin to return the pin when thethermal element cools, a tappet slidably and non-sealingly positioned insaid guideway and adapted to contact and unseat said valve element fromsaid small seat, a second spring abutted between said push pin and saidtappet, a third spring abutted between said tappet and said innerbushing and opposing said second spring, a passage formed in the outerbushing and having a relatively large valve seat formed around its innerend and spaced from said small seat by a distance about .005 inchgreater than the effective length of said valve element to be closed bythe valve element when the latter is unseated from the small seat bysaid tappet, said passage in said outer bushing being adapted to beconnected to the manifod of said engine, a fourth spring biasing saidvalve element toward said small seat, and means forming a ilow passagethrough said housing from said cavity and between said seals and adaptedat its outer end for connection to a shutter actuating pressure operateddevice.

3. A thermally actuated valve for regulating a source of abnormalpressure developed by an internal combustion engine in response to thetemperature in the cooling jacket of the engine comprising a housingadapted to be threaded into an opening in a wall of said jacket, athermally responsive element carried on the end of said housing toproject into said jacket and having a mass of thermally expansiblematerial adapted to push on a push pin positioned in a bore in the endof said housing, a recess in said housing opening to said pin, a pair ofvalve bushings arranged in end to end relation in the opposite end ofsaid recess with the outer bushing threaded into the housing andlocating the inner bushing, O-rings around said bushings forming sealsbetween the exterior of the bushings and the wall of said recess, one ofsaid bushings having a cavity formed in the end thereof opposed to theother bushing, a valve element positioned in said cavity, a guidewayextending axially through the inner of said bushings and having arelatively small valve seat around its outer end adapted to be closed bysaid valve element, a rst spring compressed between said inner bushingand said push pin, a tappet slidably and non-sealingly positioned insaid guideway and adapted to contact and unseat said valve element fromsaid small seat, a second spring abutted between said push pin and saidtappet, a passage formed in the outer bushing and having a relativelylarge valve seat formed around its inner end and spaced from said smallseat by a distance about .005 inch greater than the eliective length ofsaid valve element to be closed by the valve element when the latter isunseated from the small seat by said tappet, said passage in said outerbushing being adapted to be connected to the manifold of said engine, athird spring biasing said valve element toward said small seat, andmeans forming a flow passage from said cavity and between said seals andadapted at its outer end for connection to a shutter actuating pressureoperated device.

4. A thermally actuated valve for regulating a source of-vacuum inresponse to the temperature comprising a housing adapted to be mountedover an opening in a wall enclosing the material the temperature ofwhich is to be sensed, a thermally responsive element carried on the endof said housing to project into said wall and having a mass of thermallyexpansible material adapted to push on a push pin positioned in a borein the end of said housing, a recess in said housing opening to saidpin, an air passage opening from said recess to the outside of saidhousing, a pair of valve bushings arranged in end to end relation in theopposite end of said recess, one of said bushings having a projection onits end abutting the other bushing and forming a space between thebushings, one of said bushings having a cavity formed in the end thereofopposed to the other bushing, a valve element positioned in said cavity,a guideway extending axially through the inner of said bushings andhaving a relatively small valve seat around its outer end adapted to beclosed by said valve element, a rst spring compressed between a pointtixed relative to said housing and said push pin to return the pin whenthe thermal element cools, a tappet slidably and non-sealinglypositioned in said guideway and adapted to contact and unseat said valveelement from said small seat, a second spring abutted between said pushpin and said tappet, a third spring abutted between said tappet and saidinner bushing and opposing said second spring, a passage formed in theouter bushing and having a relatively large valve seat formed around itsinner end and spaced from said small seat by a distance about .005 inchgreater than the effective length of said valve element to be closed bythe valve element when the latter is unseated from the small seat bysaid tappet, said passage in said outer bushing being adapted to beconnected to a source of vacuum, a fourth spring biasing said valveelement toward said small seat, and means forming a iloW passage throughsaid housing from said cavity and adapted at its outer end forconnection to a pressure operated device.

5. A thermally actuated valve for regulating a source of abnormalpressure in response to temperature comprising a housing adapted to bemounted over an opening in a wall enclosing the material the temperatureof which is to be sensed, a thermally responsive element carried on theend of said housing to project into said wall and having a mass ofthermally expansible material adapted to push on a push pin positionedin a bore in the end of said housing, a recess in said housing openingto said pin, an air passage opening from said recess to the outside ofsaid housing, a pair of valve bushings arranged in end to end relationin the opposite end of said recess, one of said bushings having aprojection thereon engaging the other bushing to form a space betweenthe bushings, one of said bushings having a cavity formed in the endthereof opposed to the other bushing, a valve element positioned in saidcavity, a guideway extending axially through the inner of said bushingsand having a relatively small valve seat around its outer end adapted tobe closed by said Valve element, a rst spring compressed between a pointlixed relative to said housing and said push pin to return the pin whenthe thermal element cools, a tappet slidably and non-sealinglypositioned in said guideway and adapted to contact and unseat said valveelement from said small seat, a second spring abutted between said pushpin and said tappet, a passage formed in the outer bushing and having arelatively large valve seat formed around its inner end and spaced fromsaid small seat by a distance only slightly greater than the effectivelength of said valve element to be closed by the valve element when thelatter is unseated from the small seat by said tappet, said passage insaid outer bushing being adapted to be connected to said source ofpressure, a third spring biasing said valve element toward said smallseat, and means forming a flow passage through said housing from saidcavity and adapted at its outer end for connection to a pressureoperated device.

6. A thermostatically actuated valve comprising means forming a valvecavity with opposed large and small seats at opposite ends thereof, aball valve element positioned in said cavity and adapted toalternatively close against said seats with a movement of the order of.0015 inch, a `first spring biasing said valve element to said smallseat, a tappet positioned through said small seat to move said valveelement against said large seat, a thernio-responsive element having apush pin opposed to said tappet and extensible towards the tappet whenthe thermo-responsive element is heated, a second spring biasing saidpush pin to retracted position independently of said tappet, a thirdspring abutted between said push pin and said tappet, a fourth springbiasing said tappet toward said push pin, means connecting said smallvalve seat to the atmosphere, means adapted to connect said large seatto a source of vacuum, and means adapted to connect said valve cavity toa pressure differential actuated motor.

7. A thermostatically actuated Valve comprising means forming a Valvecavity with opposed large and small seats at yopposite ends thereof, aball valve element positioned in said cavity and adapted toalternatively close against said seats with a small movement sufficientto break the closure at either seat, a first spring biasing said valveelement to said small seat, a tappet positioned through said small seatto move said valve element against said iirst spring, athermo-responsive element having a push pin opposed to said tappet andextensible towards the tappet when the thermo-responsive element isheated, a second spring biasing said push pin to retracted positionindependently of said tappet, a third spring abutted between said pushpin and said tappet, means connecting said small valve seat to theatmosphere, means adapted to connect said large seat to a source ofabnormal pressure, and means adapted to connect said valve cavity to apressure differential actuated motor.

8. A thermostatically actuated valve comprising means forming a valvecavity with opposed large and small seats at opposite ends thereof, avalve element positioned in said cavity and adapted to alternativelyclose against said seats with a movement of the order of .O inch, a rstspring biasing said valve element to said small seat, a tappetpositioned to Imove said valve element against said large seat, athermo-responsive element having a push pin opposed to said tappet andextensible towards the tappet when the thermo-responsive element isheated, a second spring biasing said push pin to retracted positionindependently of said tappet, a third spring abutted between said pushpin and said tappet, means connecting said small valve seat to theatmosphere, means adapted to connect said large seat to a source ofvacuum, and means adapted to connect said valve cavity to a pressurediierential actuated motor.

9. A thermostatically actuated valve comprising means forming a valvecavity with opposed large and small seats at opposite ends thereof, avalve element positioned in said cavity and adapted to alternativelyclose against said seats with amovement no greater thannecessary tobreak the closure at either seat, a iirst spring biasing said valveelement to said small seat, a tappet positioned to move said valveelement toward said large seat, a thermo-responsive element having apush pin opposed to said tappet and extensible towards the tappet whenthe thermoresponsive element is heated, a second spring biasing saidpush pin to retracted position independently of said tappet, a thirdspring abutted between said push pin and said tappet, means connectingsaid small valve Vseat to the atmosphere, means adapted to connect saidlarge seat to a source of vacuum, and means adapted to connect saidvalve cavity to a pressure diierential actuated motor.

10. A thermostatically actuated valve comprising means forming a valvecavity with opposed seats at opposite ends thereof, a valve elementpositioned in said cavity and adapted to alternatively close againstsaid seats with a movement no greater than necessary to break theclosure at either seat, a iirst spring biasing said valve element to oneseat, a tappet positioned to move said valve element toward the otherseat, a thermo-responsive element containing a semi-solid thermallyexpansible material extensible towards the tappet when thethermoresponsive element is heated, a second spring biasing said tappetto retracted position, a yieldable thrust transmitting element locatedin thrust relation between said tappet and said thermo-responsiveelement, means connectv ing said rst valve seat to the atmosphere, meansadapted to connect said other seat to a source of abnormal pressure, andmeans adapted to connect said valve cavity to a pressure diierentialactuated motor.

1l. In combination with a vehicle having an internal combustion enginewith a liquid cooling system and a radiator for the cooling system, andan intake manifold as part of the engine subject to vacuum conditions inoperation, means for regulating the operation of the radiator to controlthe temperature in the cooling system comprising shutter elementsarranged to restrict the iiow of air through the radiator and movablebetween open and closed positions, means biasing said shutters to vopenposition, a pressure diierential motor connected to move said shuttersto yclosed position upon application of vacuum pressures to the motor, athermostatically actuated Valve having means forming a valve cavity withopposed seats at opposite ends thereof, a valve element positioned insaid cavity and adapted to alternatively close against said seats with asmall movement, a rst spring biasing said valve element toward one ofsaid seats, a tappet extending through said one seat to move said valveelement toward the other seat against the pressure of said first spring,a thermo-responsive element positioned in the cooling system of saidengine and having a push pin opposed to said tappet and extensibletoward the tappet when the thermoresponsive element is heated, a secondspring biasing said push pin -to retracted position independently ofsaid tappet, means forming a yieldable thust transmitting connectionbetween said push pin and said tappet, means connecting said one seat tothe atmosphere, means connecting said other seat of said valve to theintake manifold of said engine, and means connecting said valve cavityto said pressure motor.

References Cited in the tile of this patent UNITED STATES PATENTS920,883 Rui May 4, 1909 2,037,911 Larson Apr. 21, 1936 2,248,094 KysorJuly 8, 1941 2,581,582 Ferris Jan. 8, 1952 2,829,837 Willcox Apr. 8,1958 2,830,767 Herbenar Apr. 15, 1958

